Insulating and dielectric material



July 21946@ 'RLH'AvEY 2,403,657uw :s sumnne :um m-mgczn'zc u nsnxns Filed .n n. 2s. 1943 Y6 WYE E POLY VEZ E *1oz 6 FREQUENCY IN ME'GHCYUBES b'Qzgl n N gcmbob'q 'n n gcaqsww 'n u Q *t N Jnxcnlm q. Robert L. Harvey m f1. fll

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AV (mamey Patented Joly 9,1946

macs-1 PATENT INSULATING. AND DIELECTRIC MATERIAL Robert L. Harvey. Princeton, N. J.. lssignor to Radio Corporation of of Delaware Application January 29,

1 lliialni (Cl. S60-41) l My present invention relates to insulating and dielectric materials for radio currents and has for its general object to provide an improved insulat-- ing and dielectric material having lertain unique properties which render it especially suitable. for use in electrical apparatus of the type designed t handle currents of ultra-high-frequencies', including so-called centimeter waves. l

My invention will be described in connection with the accompanying drawing wherein the singlefigure comprises a group of comparative curves showing how the Q reactan (QT- resistance of certain materials changes with frequency.

'x the 60G-1.000 megacycie range.

It is also known that if two dielectric materials.

:such. for example, as polystyrene and Asilica. di-

oxide (see curve B). are mixed together, the

resulting compound will possess a Q lower than either of its constituents at any given frequency I and. like its separate constituents. will exhibit a j decrease in Q with an increase in frequency.

There are numerous applications in radio and analogous communication systems of the type utilizing ultra-high-frequencies for an insulating or dielectric material which will exhibit a con- 40 etant Q or a rising Q. with an increase in fre quency. By way of example: in a transmission line wherein loss normally increase with fr@ quency due to redistribution of the current il. e..

alone or in combination with other materials, as

"skin efiect) a material having 'a Q which increases with frequency could bc employed as dielectric and/or insulating material to compensate for such losses. A material which exhibits inflatQorarisingQ.withanincreaseinfre'V quen'cy can also be used to advantage. either the dielectric medium' in electric capacitors .of various types and ratings. By way of example. auch capacitors could be used in installations wherein it is desired-to vary the selectivity ofthe America. a con cration""""` Masern! no. 413.931

, 2 tuned circuits in a desired manner. with fre fluency;

Accordingly. a speciflc-obiect of my invention is to provide an improved insulating and dielectric material for currents of radio frequencies,

and one which shall exhibit a ilat Q or. alternatively. a rising "Q with an increase in fre quency. and this, too. at frequencies of upwards of nve million cycles (5 megacycles) per second.

A'Another and important object of my present invention is to achieve the aforesaid highly deairable and unique characteristics in a material having satisfactory heat resisting properties.

The foregoing and other objects are achieved in accordance with my invention by the addition, to moldable types of insulating compounds. prior to the molding operation, of a metal of low specific resistance. such for example. as copper or silver.' in o. finely divided state. The speciilcl re- In m1571118 my invention into eil'ect I prefer to employ polystyrene as the basic insulating ingredient because of its relatively high "Q" value.

though I may employ other thermoplastic or thermosetting insulating materials. such for example as the phenol aldehyde, urea. aldehyde and.

conductive compound which exhibits a suhstantially constant Q over a frequency range of from.

say. 5 to 400 megacycles. In order to achieve a Q which increases with frequency I employ a greater Percentage of powdered metal.` Thus, referring to l curve D.I have found that the addition of 35 by weight. of powdered copper to polystyrene results in a compound which exhibits o. uniformly Q in the 5 to 400 megacycle band. Curves E and F' show that over the same frequency range o. somewhat lower Q, but one which nevertheless increases with frequency, is achieved when the percentage of copper inthe compound is lncreased to and 70% respectively.

I have found that the addition of the powdered 5 lr'netal to the conventional insulating materials increases the usable temperature range of such materials. Thus, in the case of polystyrene the usable temperature range is increased from Cito, say. C.

As a result ci' my work with these dielectric OFFICE compounds over a. iride frequency range I have reason to believe that the slope oi' the curves C, D. E and F xeman substantially the same as indi-A cated m the drawing at irequencies of the order of several thousand megacycies. but owingto the possibility of error in making the necessary :new

'urement; at these frequencies with present day npparatus and technique. I have omitted such representation from the drawing.

I claim:

An eiearioai insulating and dielectric medium consisting ot polystyrene and distributed therethrough a neiy divided meta! selected from the group consisting of copper and silver in the pro portion of from 10 percent to 35 percent by weight o! the polystyrene. said medium exhibiting n ratio o! actance to resistance within the frequency range o! from 5 megacycies per second to 1.000 megacycles per second which has a. value at least. as great at the higher of said frequencies as at the lower of said frequencies.

ROBERT L HARVEY. 

